package com.hrp.analyzer.util.io;

/**
 * 代码移植自<a href="https://github.com/biezhi/blade">blade</a><br>
 * 快速缓冲，将数据存放在缓冲集中，取代以往的单一数组
 *
 * @author biezhi, looly
 * @date 1.0
 */
public class FastByteBuffer {

  /**
   * 一个缓冲区的最小字节数
   */
  private final int minChunkLen;
  /**
   * 缓冲集
   */
  private byte[][] buffers = new byte[16][];
  /**
   * 缓冲数
   */
  private int buffersCount;
  /**
   * 当前缓冲索引
   */
  private int currentBufferIndex = -1;
  /**
   * 当前缓冲
   */
  private byte[] currentBuffer;
  /**
   * 当前缓冲偏移量
   */
  private int offset;
  /**
   * 缓冲字节数
   */
  private int size;

  public FastByteBuffer() {
    this.minChunkLen = 1024;
  }

  public FastByteBuffer(int size) {
    this.minChunkLen = Math.abs(size);
  }

  /**
   * 分配下一个缓冲区，不会小于1024
   *
   * @param newSize 理想缓冲区字节数
   */
  private void needNewBuffer(int newSize) {
    int delta = newSize - size;
    int newBufferSize = Math.max(minChunkLen, delta);

    currentBufferIndex++;
    currentBuffer = new byte[newBufferSize];
    offset = 0;

    // add buffer
    if (currentBufferIndex >= buffers.length) {
      int newLen = buffers.length << 1;
      byte[][] newBuffers = new byte[newLen][];
      System.arraycopy(buffers, 0, newBuffers, 0, buffers.length);
      buffers = newBuffers;
    }
    buffers[currentBufferIndex] = currentBuffer;
    buffersCount++;
  }

  /**
   * 向快速缓冲加入数据
   *
   * @param array 数据
   * @param off   偏移量
   * @param len   字节数
   * @return 快速缓冲自身 @see FastByteBuffer
   */
  public FastByteBuffer append(byte[] array, int off, int len) {
    int end = off + len;
    if ((off < 0) || (len < 0) || (end > array.length)) {
      throw new IndexOutOfBoundsException();
    }
    if (len == 0) {
      return this;
    }
    int newSize = size + len;
    int remaining = len;

    if (currentBuffer != null) {
      // first try to fill current buffer
      int part = Math.min(remaining, currentBuffer.length - offset);
      System.arraycopy(array, end - remaining, currentBuffer, offset, part);
      remaining -= part;
      offset += part;
      size += part;
    }

    if (remaining > 0) {
      // still some data left
      // ask for new buffer
      needNewBuffer(newSize);

      // then copy remaining
      // but this time we are sure that it will fit
      int part = Math.min(remaining, currentBuffer.length - offset);
      System.arraycopy(array, end - remaining, currentBuffer, offset, part);
      offset += part;
      size += part;
    }

    return this;
  }

  /**
   * 向快速缓冲加入数据
   *
   * @param array 数据
   * @return 快速缓冲自身 @see FastByteBuffer
   */
  public FastByteBuffer append(byte[] array) {
    return append(array, 0, array.length);
  }

  /**
   * 向快速缓冲加入一个字节
   *
   * @param element 一个字节的数据
   * @return 快速缓冲自身 @see FastByteBuffer
   */
  public FastByteBuffer append(byte element) {
    if ((currentBuffer == null) || (offset == currentBuffer.length)) {
      needNewBuffer(size + 1);
    }

    currentBuffer[offset] = element;
    offset++;
    size++;

    return this;
  }

  /**
   * 将另一个快速缓冲加入到自身
   *
   * @param buff 快速缓冲
   * @return 快速缓冲自身 @see FastByteBuffer
   */
  public FastByteBuffer append(FastByteBuffer buff) {
    if (buff.size == 0) {
      return this;
    }
    for (int i = 0; i < buff.currentBufferIndex; i++) {
      append(buff.buffers[i]);
    }
    append(buff.currentBuffer, 0, buff.offset);
    return this;
  }

  public int size() {
    return size;
  }

  public boolean isEmpty() {
    return size == 0;
  }

  /**
   * 当前缓冲位于缓冲区的索引位
   *
   * @return {@link #currentBufferIndex}
   */
  public int index() {
    return currentBufferIndex;
  }

  public int offset() {
    return offset;
  }

  /**
   * 根据索引位返回缓冲集中的缓冲
   *
   * @param index 索引位
   * @return 缓冲
   */
  public byte[] array(int index) {
    return buffers[index];
  }

  public void reset() {
    size = 0;
    offset = 0;
    currentBufferIndex = -1;
    currentBuffer = null;
    buffersCount = 0;
  }

  /**
   * 返回快速缓冲中的数据
   *
   * @return 快速缓冲中的数据
   */
  public byte[] toArray() {
    int pos = 0;
    byte[] array = new byte[size];

    if (currentBufferIndex == -1) {
      return array;
    }

    for (int i = 0; i < currentBufferIndex; i++) {
      int len = buffers[i].length;
      System.arraycopy(buffers[i], 0, array, pos, len);
      pos += len;
    }

    System.arraycopy(buffers[currentBufferIndex], 0, array, pos, offset);

    return array;
  }

  /**
   * 返回快速缓冲中的数据
   *
   * @param start 逻辑起始位置
   * @param len   逻辑字节长
   * @return 快速缓冲中的数据
   */
  public byte[] toArray(int start, int len) {
    int remaining = len;
    int pos = 0;
    byte[] array = new byte[len];

    if (len == 0) {
      return array;
    }

    int i = 0;
    while (start >= buffers[i].length) {
      start -= buffers[i].length;
      i++;
    }

    while (i < buffersCount) {
      byte[] buf = buffers[i];
      int c = Math.min(buf.length - start, remaining);
      System.arraycopy(buf, start, array, pos, c);
      pos += c;
      remaining -= c;
      if (remaining == 0) {
        break;
      }
      start = 0;
      i++;
    }
    return array;
  }

  /**
   * 根据索引位返回一个字节
   *
   * @param index 索引位
   * @return 一个字节
   */
  public byte get(int index) {
    if ((index >= size) || (index < 0)) {
      throw new IndexOutOfBoundsException();
    }
    int ndx = 0;
    while (true) {
      byte[] b = buffers[ndx];
      if (index < b.length) {
        return b[index];
      }
      ndx++;
      index -= b.length;
    }
  }

}
